The present invention relates in general to a cartridge assembly, and more particularly, to a cartridge assembly of unitary construction adapted for projecting loads therefrom such as pyrotechnic flares, smoke flares, chaff rounds, and the like, which cartridge assembly includes an internally formed integral seal arranged at one end thereof for alternatively sealing a removable impulse cartridge and protective plug therein to prevent moisture contamination of the load, and including a rupturable closure arranged at the other end thereof through which the load is projected and having means to facilitate the alignment and insertion of the rupturable closure therein and provide a moisture proof seal.
Anti-aircraft missiles having guidance systems are commonly designed to home in on infrared energy generated by a turbojet engine tailpipe or exhaust plume. Such missiles are sensitive to infrared energy in precise preselected wavelengths which are generated by the hot tailpipe or exhaust plume. These missiles are commonly counter measured by launching a high temperature source such as a pyrotechnic flare from the aircraft which will generate infrared energy in that portion of the spectrum to which the missile is sensitive. The missile, then breaks its lock from the aircraft and locks in on the decoy infrared source and permits the aircraft to escape.
Known pyrotechnic flare cases are generally constructed from a metallic billet drawn into the form of a hollow casing which receives an internal slidable piston arranged adjacent to a pyrotechnic mixture. An impulse cartridge is inserted within an open end of the casing adjacent the piston and ignited to propel the pyrotechnic mixture out of the casing by movement of the piston due to the resulting build-up of gas pressure therebehind. It is well-known that these pyrotechnic mixtures must be sealed from contamination from moisture which could react with the mixture to result in reduced or unsatisfactory performance. In addition, it is also well-known that the pyrotechnic flare must be rendered safe during storage by removal of the impulse cartridge and the insertion of a blank plug to seal the open end of the casing. To this end, the open end of the metallic casing of the known pyrotechnic flares have been individually machined to include a circumscribing groove adapted to receive an O-ring as a seal member for either the impulse cartridge or blank plug.
The manufacture of these pyrotechnic flare cases from metallic billets drawn to form a hollow casing therefrom, and machined at one end to provide a groove for receiving an O-ring, has been both expensive and labor intensive. In order to achieve a more economic advantage in the construction of these pyrotechnic flare cases, the prior art has recognized the advantage of molding the hollow casing from plastic material. However, the molding of a unitary hollow casing from plastic material to include an internal circumscribing groove for retaining an O-ring therein requires the use of expensive molds having movable pins and parts. To avoid the necessity of constructing expensive and complicated molds, the construction of a multiple component plastic casing has been fabricated. However, such casing requires the joining of the plastic components along parting lines which are a source of failure of the pyrotechnic flare due to cracking, poor bonding, penetration by moisture, as well as increasing the manufacturing costs. In order to overcome these disadvantages resulting from the construction of a multi-component plastic casing, the prior art has constructed the open end of the casing to include a circumscribing planar surface having a plastic flashing adapted to provide an interference seal with the impulse cartridge and/or blank plug. At best, this interference fit is not capable of reproducibility or reliability. Moreover, this interference fit is often eliminated due to temperature changes and/or the repeated insertion of either the impulse cartridge or blank plug. For example, the blank plug, which is tapered, would often stretch out the plastic flashing which would retain its new dimension thereby preventing it from affecting a seal with the impulse cartridge.
In addition to providing a seal for the impulse cartridge or blank plug at one end of the plastic casing, it is required to provide a moisture sealed rupturable closed end through which the pyrotechnic mixture will be ejected during use of the pyrotechnic flare. The known pyrotechnic flare with aluminum case has used a plastic rectangular end cap which was manually inserted into its rectangular opening formed at one end of the hollow casing. Using an O-ring to provide the seal, the end cap, after being inserted into the casing to its proper depth, was locked in place by two plastic pins inserted through holes in the metal case and was sealed using an appropriate sealant such as Silicone adhesive. The insertion of the plastic pins and sealing operation required labor-intensive effort. Another disadvantage of the existing assembly is that the O-ring used in the end cap must be assembled by passing the holes at the same level that the seal will function. Potential damage to the O-ring caused by burrs and sharp edges often results in sealing failure.